Date: Sat, 21 Dec 2013 11:15:52 -0800 From: John-Mark Gurney <jmg@funkthat.com> To: Guy Yur <guyyur@gmail.com> Cc: freebsd-net@freebsd.org, freebsd-arm@freebsd.org Subject: Re: 10.0-RC1: net/mpd5 crashes in NgMkSockNode due to stack alignment on ARM EABI Message-ID: <20131221191552.GE99167@funkthat.com> In-Reply-To: <CAC67Hz82VBT1_BBH6E18ycDxUdWbgFcahNo1W0kH-TcH7iB=8Q@mail.gmail.com> References: <CAC67Hz82VBT1_BBH6E18ycDxUdWbgFcahNo1W0kH-TcH7iB=8Q@mail.gmail.com>
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Guy Yur wrote this message on Sat, Dec 21, 2013 at 19:24 +0200:
> I am running 10.0-RC1 on the BeagleBone Black and the net/mpd5 port is
> crashing in libnetgraph NgMkSockNode due to stack alignment.
>
> 10.0-RC1 World and kernel were compiled in a VirtualBox VM running
> 9.2-RELEASE-p2 i386.
> clang and ARM_EABI used as the default make options.
>
> Added prints in NgMkSockNode show rbuf is aligned on 2-byte and not
> 4-byte which is needed to access ni->id (a uint32_t).
>
> ni = 0xbfffe87a
> rbuf = 0xbfffe842
> sizeof(resp->header) = 56
>
>
> (gdb) bt
> #0 0x201529a0 in NgMkSockNode (name=<value optimized out>, csp=0xbfffe95c,
> dsp=0xbfffe958) at /usr/src/lib/libnetgraph/sock.c:134
> #1 0x00037b9c in MppcTestCap () at ccp_mppc.c:754
> #2 0x0007c1f4 in main (ac=4, av=0xbfffeb90) at main.c:248
> #3 0x0000d1b0 in __start (argc=4, argv=0xbfffeb90, env=0xbfffeba4,
> ps_strings=<value optimized out>, obj=<value optimized out>,
> cleanup=<value optimized out>) at /usr/src/lib/csu/arm/crt1.c:115
> #4 0x203e9dc0 in _thr_ast (curthread=0x200fd000)
> at /usr/src/lib/libthr/thread/thr_sig.c:265
>
>
> Putting rbuf in a union with struct ng_mesg sorted the alignment to
> 4-byte and mpd5 didn't crash.
> I attached the changes I used to test mpd5 doesn't crash with correct alignment.
The patch looks correct, but lets make sure that the -net people don't
have an issue with it...
I've reattached Guy's patch for review.
Guy, bug me in a week or so if I haven't committed it, and I will...
Thanks for tracking this down.
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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Index: lib/libnetgraph/sock.c
===================================================================
--- lib/libnetgraph/sock.c (revision 259250)
+++ lib/libnetgraph/sock.c (working copy)
@@ -111,8 +111,11 @@
/* Save node name */
strlcpy(namebuf, name, sizeof(namebuf));
} else if (dsp != NULL) {
- u_char rbuf[sizeof(struct ng_mesg) + sizeof(struct nodeinfo)];
- struct ng_mesg *const resp = (struct ng_mesg *) rbuf;
+ union {
+ u_char rbuf[sizeof(struct ng_mesg) + sizeof(struct nodeinfo)];
+ struct ng_mesg res;
+ } res;
+ struct ng_mesg *const resp = (struct ng_mesg *) res.rbuf;
struct nodeinfo *const ni = (struct nodeinfo *) resp->data;
/* Find out the node ID */
@@ -123,7 +126,7 @@
NGLOG("send nodeinfo");
goto errout;
}
- if (NgRecvMsg(cs, resp, sizeof(rbuf), NULL) < 0) {
+ if (NgRecvMsg(cs, resp, sizeof(res.rbuf), NULL) < 0) {
errnosv = errno;
if (_gNgDebugLevel >= 1)
NGLOG("recv nodeinfo");
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